Dr Kupe: Juvenile Idiopathic Arthritis

Definitions
Defined by the presence of arthritis
  - in > 1 joint,
  - for < 6 weeks,
  - in a child < 16 yrs of age at onset
  - to the exclusion of known causes of arthritis

Pathophysiology

involves elements of B & T-cell
?viral trigger(eg Rubella)

Aetiology
unknown(autoimmune)
strong association with HLA

Epidemiology
Commonest childhood rheumatoid disease
Incidence: 20/100,000 children
Bimodal peaks: 2 & 9 y.o
Commoner in whites
Male:Female = 1:2
95% are distinct from adult Rheumatoid Arhtritis
>50% persist into adulthood

Classification(subtype)
Based on ILAR classification

Classification	Articular pattern	Extra-articular pattern	Lab abnormalities
Oligoarthritis (persistent)(49%)	1-4(max) joints involved; knee, ankle or wrist most common	Chronic anterior uveitis 20%, leg length descrepancy	ANA+
Oligoarthritis (extended) (8%)	>4 joints after first 6months. Asymmetrical distribution	Chronic anterior uveitis 20% asymmetrical growth, prognosis moderate	ANA+
Polyarthritis (RF-ve) (16%)	Symmetrical, marked finger involment, cervical spine, temporomandibular joint	Low grade fever anterior uveitis 5%, late reduction of growth rate prognosis moderate
Polyarthritis (RF+ve) (4%)	Symmetrical, finger involvement	Rheumatoid nodules 10%, prognosis poor	RF+ (long term)
Systemic arthritis (9%)	Oligo or polyarthrits, athralgia/myalgia but iniatially no arthritis	Acute illness, malaise, high daily fever initially >2wk, evanescent salmon-pink, macular-rash, lymphadenopathy, hepatosplenomegaly, serosistis may cause Macrophage Activation Syndrome (MAS) Prognosis variable to poor	Anaemia, raised neutrophills, and platelets, high acute-phase reactants
Psoriatic arthritis (7%)	Artritis and psoriasis and 2 of: dactylitis, pitting or onycholosis, family hx of psoriasis	Psoriasis, nail-pitting/distrophy, chronic anterior uveitis 20% Prognosis moderate
Enthetesis-related arthritis (7%)	Lower limb, large joint arthritis initially, mild lumbar spine or sacroiliac involvement later on	arthritis AND/OR enthetesis with 2 of: sacroiliac tenderness, inflammatory spinal pain, HLA-B27+family hx, anterior uveitis, onser in a boy >6 y,o	HLA B27+ ANA negative
Undifferentiated (1%)	Overlapping articular and extraarticular patterns between >2 subtypes or insufficient criteria for subclassification	Prognosis variable

Uveitis
- 20% of oligo patients
- anterior, bilateral
- young, female, ANA+ve
- insidous, asymptomatic
- does not parallel course of joint disease
- Chronic uveitis- blindness in 12%, occurs within 4-7 years of disease
- Poor prognosis: uveitis at presentation, severe at onset, persisting disease activity
- Complications : synechiae 62%, band keratopathy (37%), Cataract (40%), Glaucoma (18%)

Salmon-pink rash in systemic onset arthritis

Investigation
FBC
ESR, CRP
U&E
LFT
Autoantibodies, RF
ANA - greater risk of eye damage in oligoarthritis
X-Ray
MRI
Eye test

Management
Principles
- objective: control pain, prevent deformity, promote normal growth
- Multidisciplinary: Paediatric rheumatologust, PT/OT therapist, opthalmologist, orthopedist, cardiologist, nephrologist, diatician

Pharmacotherapy
1st line
  - NSAIDS - Naproxen(15mg/kg/d), Indomethacin (1-3mg/kg/d), Ibuprofen (40-60mg/kg/d), Diclofenac (1-3mg/kg/d), COX-2 inhibitor
     well tolerated,effective in 30% of JIA, beware of GI toxicity & pseudo-porphyrria
  - Intra-articular steroid injection
2nd line
  - DMARDs: Methotrexate, Sulfasalazine, Leflunomide, systemic corticosteroid, Gold Compound, D-Penicillamine
  - Cytotoxic Agent- Cyclosporine, Azathioprine, Cyclophosphamide
  - IVIG
  - Systemic Corticosteroids
3rd line
  - (Biologic Agents) – TNF-a-inhibitors *Etanercept, Infliximab, Adalinumab), IL-1r-antagonist, IL-6r mAb, co-stimulatory molecule blockade,

Other treatment
  - Autologous stem cell transplantation, thalidomide

Uveitis therapy
  - early detection
  - Corticosteroid- Drops Oral prednisone, IV pulse therapy, Subtenon injections
  - NSAIDs, Methotrexate, Cyclosporine

Non-drug therapy
- Physical therapy- daily exercise program
- Occupational therapy: upper limb function, ADLS, splints
- Heat/Cold

Outcome Measures
Core set for trials in JIA
- active joint count
- number of joints with limited range of movement
- Physician global assessment of severity
- Patient global assessment of severity
- ESR
- Functional Assessment

Definition of improvement
- 30% improved in at least 3/6 core set
- no more than 1 variable show worsening by >30%